THE BIOLOGICAL SIGNIFICANCE OF TOBACCO-SPECIFIC N-NITROSAMINES - SMOKING AND ADENOCARCINOMA OF THE LUNG

In the U.S., there has been a steeper rise of the incidence of lung ad enocarcinoma than of squamous cell carcinoma of the lung among cigaret te smokers. Since 1950, the percentage of all cigarettes sold that had filter tips increased from 0.56 to 92% in 1990 and to 97% in 1990. Th e tobacco of the filter cigarettes is richer in nitrate than that of t he nonfilter cigarettes manufactured in past decades. Because the smok er of cigarettes with lower nicotine yield tends to smoke more intense ly and to inhale the smoke more deeply than the smoker of plain cigare ttes, the peripheral lung is exposed to higher amounts of nitrogen oxi des, nitrosated compounds, and lung-specific smoke carcinogens. It is our working hypothesis that more intense smoking, deeper inhalation of the smoke, and higher smoke delivery of the organ-specific lung carci nogen NNK to the peripheral lung are major contributors to the increas ed risk of cigarette smokers for lung adenocarcinoma. Bioassay data an d biochemical studies in support of this concept are discussed.